1 How long have you studied at your school?
I have studied for 8 years at my school.
2 How long have you known your best friend?
I have known my best friend for 10 years.
3 How long have you had your pet?
I have had my pet since I was 6.
4 How long has your father known your mother?
He has known my mother since his childhood.
5 How long have your family lived in your flat (house)?
We have lived in our flat for 12 years.